/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
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/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.search.suggest.phrase;

import org.opensearch.common.xcontent.XContentParser;

import java.io.IOException;

import static org.hamcrest.Matchers.instanceOf;

public class LinearInterpolationModelTests extends SmoothingModelTestCase {

    @Override
    protected SmoothingModel createTestModel() {
        return createRandomModel();
    }

    static LinearInterpolation createRandomModel() {
        double trigramLambda = randomDoubleBetween(0.0, 10.0, false);
        double bigramLambda = randomDoubleBetween(0.0, 10.0, false);
        double unigramLambda = randomDoubleBetween(0.0, 10.0, false);
        // normalize so parameters sum to 1
        double sum = trigramLambda + bigramLambda + unigramLambda;
        return new LinearInterpolation(trigramLambda / sum, bigramLambda / sum, unigramLambda / sum);
    }

    /**
     * mutate the given model so the returned smoothing model is different
     */
    @Override
    protected LinearInterpolation createMutation(SmoothingModel input) {
        LinearInterpolation original = (LinearInterpolation) input;
        // swap two values permute original lambda values
        switch (randomIntBetween(0, 2)) {
            case 0:
                // swap first two
                return new LinearInterpolation(original.getBigramLambda(), original.getTrigramLambda(), original.getUnigramLambda());
            case 1:
                // swap last two
                return new LinearInterpolation(original.getTrigramLambda(), original.getUnigramLambda(), original.getBigramLambda());
            case 2:
            default:
                // swap first and last
                return new LinearInterpolation(original.getUnigramLambda(), original.getBigramLambda(), original.getTrigramLambda());
        }
    }

    @Override
    void assertWordScorer(WordScorer wordScorer, SmoothingModel in) {
        LinearInterpolation testModel = (LinearInterpolation) in;
        LinearInterpolatingScorer testScorer = (LinearInterpolatingScorer) wordScorer;
        assertThat(wordScorer, instanceOf(LinearInterpolatingScorer.class));
        assertEquals(testModel.getTrigramLambda(), (testScorer).trigramLambda(), 1e-15);
        assertEquals(testModel.getBigramLambda(), (testScorer).bigramLambda(), 1e-15);
        assertEquals(testModel.getUnigramLambda(), (testScorer).unigramLambda(), 1e-15);
    }

    @Override
    protected SmoothingModel fromXContent(XContentParser parser) throws IOException {
        return LinearInterpolation.fromXContent(parser);
    }
}
